One of the most curious scenes I have ever
seen in animal behavioris one of a bird (a cardinal) feeding
insects to "minnows" in a small pond (Fig 1).

Fig.1. In a small pond, a cardinal feeds
minnows, which rose to the surface looking for food. During several weeks
the bird fed them, probably because his nest had been destroyed.&nbsp;

Taken from Animal Behavior, N. Tinbergen,
Time Inc, 1966.

Touching, if it were not for one reason:
the bird did not "pity" nor showed "solidarity" with the hungry fish, sharing
the food. What probably happened is that, having lost his nestlings, the
bird inadequately responded to a dominant parental instinct, that is, the
sight of stimuli similar to his nestling (small open mouths) elicited an
inborn and stereotpypic behavior, known in ethology as FAP or instictive
mechanical acts. FAP are stereotypic and inborn behavior. They are genetically
determined and present a complex interaction with environmental stimuli.
The Dutch ethologist Niko Tinbergen, Nobel Prize, was one of the first
to study FAP in vertebrates, such as seagulls, ducks and so on.

A classical example of FAP studied by Tinbergen
is the goose behavior of picking eggs up. When the female notices an egg
outside the nest (key stimulus) , it begins a repeated movement to drag
the egg with its beak and neck. However if the egg slides off or if it
is removed by the researcher, the goose continues to repeat the stereotypic
movements even if the egg is absent, until it reaches the nest, when then
it does it all over again. Therefore, FAP seems to correspond to a fixed
neural circuitry elicited by the overall trigger stimuli.

Fig. 2. Female goose behavior of picking
eggs up. When it sees an egg outside the nest (key stimulus), it begins
a repeated movement of dragging the egg with its beak and neck. However,
if the eggs slides off or if it is removed by the researcher, the goose
continues to repeat the stereotypic movements even if the egg is absent,
until it reaches the nest, when then it does it all over again. FAP seems
to correspond to a fixed neural circuitry elicited by the overall trigger
stimuli.

Human beings also display various instictive
movements, which generally manifest themselves soon after birth. They are
called behavioral reflexes. One example is the characteristic prehensive
reflex of the hand of new-borns, who firmly hold any object.Quantitative measures showed that infants
apply more strength if they touch hair. This FAP appeared by evolution
among primates, so that the infant can hold to the mother's hair and do
not fall off when she moves briskly. Given a rope, new-borns hold firmly
and remain suspended by themselves.

Fig. 3. Human beings also display several
instinctive motor behaviors, which generally manifestthemselves immediately after birth. They
are called behavioral reflexes, such as when a new-born firmly holds a
rope and he can be lifted. This behavior appeared in evolution among the
primates, so that infants hold to the mothers' hair and do not fall off
when she moves briskly.